The present invention relates to an electric rotating machine including a casing, two rotors and a stator common to the rotors which are disposed within the casing.
U.S. Pat. No. 6,114,784, corresponding to Japanese Patent Application First Publication No. 2000-14086, discloses a multi-layer motor including a cylindrical stator and two cylindrical rotors which are disposed inside and outside the stator. The stator and the inner and outer rotors form a three-layered structure. The stator is supplied with compound current for separately driving the inner and outer rotors. The inner and outer rotors are independently operated by controlling the compound current, thereby enabling separate rotation outputs from the inner and outer rotors, respectively.